Molten-salt battery
Molten-salt batteries are a class of battery that uses molten salts as an electrolyte and offers both a high energy density and a high power density. Traditional non-rechargeable thermal batteries can be stored in their solid state at room temperature for long periods of time before being activated by heating. Rechargeable liquid-metal batteries are used for industrial power backup, special electric vehicles[citation needed]and for grid energy storage, to balance out intermittent renewable power sources such as solar panels and wind turbines.
History
Thermal batteries originated during
Rechargeable configurations
Since the mid-1960s much development work has been undertaken on
Sodium–sulfur
The sodium–sulfur battery (NaS battery), along with the related lithium–sulfur battery employs cheap and abundant electrode materials. It was the first alkali-metal commercial battery. It used liquid sulfur for the positive electrode and a ceramic tube of beta-alumina solid electrolyte (BASE). Insulator corrosion was a problem because they gradually became conductive, and the self-discharge rate increased.
Because of their high specific power, NaS batteries have been proposed for space applications.[6][7] An NaS battery for space use was successfully tested on the Space Shuttle mission STS-87 in 1997,[8] but the batteries have not been used operationally in space. NaS batteries have been proposed for use in the high-temperature environment of Venus.[8]
A consortium formed by Tokyo Electric Power Co. (TEPCO) and NGK Insulators Ltd. declared their interest in researching the NaS battery in 1983, and became the primary drivers behind the development of this type ever since. TEPCO chose the NaS battery because its component elements (sodium, sulfur and ceramics) are abundant in Japan. The first large-scale field testing took place at TEPCO's Tsunashima substation between 1993 and 1996, using 3 × 2 MW, 6.6 kV battery banks. Based on the findings from this trial, improved battery modules were developed and were made commercially available in 2000. The commercial NaS battery bank offers:
- Capacity : 25–250 kWh per bank
- Efficiency of 87%
- Lifetime of 2,500 cycles at 100% depth of discharge (DOD), or 4,500 cycles at 80% DOD
Sodium–nickel chloride (Zebra) battery
A lower-temperature[9] variant of molten-salt batteries was the development of the ZEBRA (originally, "Zeolite Battery Research Africa"; later, the "Zero Emissions Batteries Research Activity") battery in 1985, originally developed for electric vehicle applications.[10][11] The battery uses NaNiCl
2 with Na+-beta-alumina ceramic electrolyte.[12]
The NaNiCl
2 battery operates at 245 °C (473 °F) and uses molten
4 and Na are liquid at the operating temperature, a sodium-conducting β-alumina ceramic is used to separate the liquid sodium from the molten NaAlCl
4. The primary elements used in the manufacture of these batteries have much higher worldwide reserves and annual production than lithium.[13]
It was invented in 1985 by the Zeolite Battery Research Africa Project (ZEBRA) group at the
The ZEBRA's liquid electrolyte freezes at 157 °C (315 °F), and the normal operating temperature range is 270–350 °C (520–660 °F). Adding iron to the cell increases its power response.
In 2010 General Electric announced a Na-NiCl
2 battery that it called a sodium–metal halide battery, with a 20-year lifetime. Its cathode structure consists of a conductive nickel network, molten salt electrolyte, metal current collector, carbon felt electrolyte reservoir and the active sodium–metal halide salts.[19][20] In 2015, as a result of a global restructuring, the company abandoned the project.[21] In 2017 Chinese battery maker Chilwee Group (also known as Chaowei) created a new company with General Electric (GE) to bring to market a Na-NiCl battery for industrial and energy storage applications.[22]
When not in use, Na-NiCl
2 batteries are typically kept molten and ready for use because if allowed to solidify they typically take twelve hours to reheat and charge.[23] This reheating time varies depending on the battery-pack temperature, and power available for reheating. After shutdown a fully charged battery pack loses enough energy to cool and solidify in five-to-seven days depending on the amount of insulation.[citation needed]
Sodium metal chloride batteries are very safe; a thermal runaway can be activated only by piercing the battery and also, in this unlikely event, no fire or explosion will be generated. For this reason and also for the possibility to be installed outdoor without cooling systems, make the sodium metal chloride batteries very suitable for the industrial and commercial energy storage installations.
In 2014 researchers identified a liquid sodium–cesium alloy that operates at 50 °C (122 °F) and produced 420 milliampere-hours per gram. The new material was able to fully coat, or "wet," the electrolyte. After 100 charge/discharge cycles, a test battery maintained about 97% of its initial storage capacity. The lower operating temperature allowed the use of a less-expensive polymer external casing instead of steel, offsetting some of the increased cost of cesium.[26]
Innovenergy in
Liquid-metal batteries
Professor
The technology was proposed in 2009 based on magnesium and antimony separated by a molten salt.[29][30][31] Magnesium was chosen as the negative electrode for its low cost and low solubility in the molten-salt electrolyte. Antimony was selected as the positive electrode due to its low cost and higher anticipated discharge voltage.
In 2011, the researchers demonstrated a cell with a lithium anode and a lead–antimony cathode, which had higher ionic conductivity and lower melting points (350–430 °C).[28] The drawback of the Li chemistry is higher cost. A Li/LiF + LiCl + LiI/Pb-Sb cell with about 0.9 V open-circuit potential operating at 450 °C had electroactive material costs of US$100/kWh and US$100/kW and a projected 25-year lifetime. Its discharge power at 1.1 A/cm2 is only 44% (and 88% at 0.14 A/cm2).
Experimental data shows 69% storage efficiency, with good storage capacity (over 1000 mAh/cm2), low leakage (< 1 mA/cm2) and high maximal discharge capacity (over 200 mA/cm2).[32] By October 2014 the MIT team achieved an operational efficiency of approximately 70% at high charge/discharge rates (275 mA/cm2), similar to that of pumped-storage hydroelectricity and higher efficiencies at lower currents. Tests showed that after 10 years of regular use, the system would retain about 85% of its initial capacity.[33] In September 2014, a study described an arrangement using a molten alloy of lead and antimony for the positive electrode, liquid lithium for the negative electrode; and a molten mixture of lithium salts as the electrolyte.
A recent innovation is the PbBi alloy which enables lower melting point lithium-based battery. It uses a molten salt electrolyte based on LiCl-LiI and operates at 410 °C.[34]
Ionic liquids have been shown to have prowess for use in rechargeable batteries. The electrolyte is pure molten salt with no added solvent, which is accomplished by using a salt having a room temperature liquid phase. This causes a highly viscous solution, and is typically made with structurally large salts with malleable lattice structures.[35]
Thermal batteries (non-rechargeable)
Technologies
Thermal batteries use an electrolyte that is solid and inactive at ambient temperatures. They can be stored indefinitely (over 50 years) yet provide full power in an instant when required. Once activated, they provide a burst of high power for a short period (a few tens of seconds to 60 minutes or more), with output ranging from
One design uses a fuze strip (containing barium chromate and powdered zirconium metal in a ceramic paper) along the edge of the heat pellets to initiate the electrochemical reaction. The fuze strip is typically fired by an electrical igniter or squib which is activated with an electric current.
Another design uses a central hole in the middle of the battery stack, into which the high-energy electrical igniter fires a mixture of hot gases and
In the 1980s
More recently, other lower-melting, eutectic electrolytes based on
Uses
Thermal batteries are used almost exclusively for military applications, notably for nuclear weapons
See also
- Primary cell
- Secondary cell
- Smart grid
- Flow battery
- Carnot battery
- List of battery types
References
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- Argonne National LaboratoriesReport ANL-78-94 (1980); and Report ANL-79-39 (1979).
- ^ T.M. O'Sullivan, C.M. Bingham, and R.E. Clark, "Zebra battery technologies for all electric smart car", International Symposium on Power Electronics, Electrical Drives, Automation and Motion, SPEEDAM 2006, IEEE, 23–26 May 2006. Retrieved 12 June 2018
- ^ Buchmann, Isidor (August 2011). "Weird and Wonderful Batteries: But Will the Inventions Survive Outside the Laboratory?". Batteries in a Portable World. Retrieved 30 November 2014.
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Intermediate and room-temperature liquid metal batteries, circumventing complex thermal management as well as issues related to sealing and corrosion, are emerging as a novel energy system for widespread implementation
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- ^ W. Auxer, "The PB Sodium Sulfur Cell for Satellite Battery Applications", 32nd International Power Sources Symposium, Cherry Hill, NJ, June 9–12, 1986, Proceedings Volume A88-16601, 04-44, Electrochemical Society, Inc., Pennington, NJ, pp. 49–54.
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- ^ 7.6 The Sodium Nickel Chloride "Zebra" Battery, Meridian International Research, 2006, p. 104-112. Accessed 2 August 2017.
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- ^ "GE Launches Durathon Sodium–Metal Halide Battery for UPS Market". Green Car Congress. 2010-05-18. Retrieved 2012-04-24.
- ^ "GE to Manufacture Molten Salt Sodium Nickel Chloride Batteries for Stationary Electricity Storage Applications".
- ^ "GE Reboots Its Storage Business With a Lithium-Ion Battery and Downstream Services". 2015-04-28.
- ^ "Joint Venture to bring sodium nickel battery to market | www.bestmag.co.uk". www.bestmag.co.uk. 6 January 2017.
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